Abstract
A binning scheme is proposed for D→K+π−π−π+ phase space that will improve the sensitivity of a B−→DK− analysis to the angle γ of the Cabibbo-Kobayashi-Maskawa Unitarity Triangle. The scheme makes use of amplitude models recently reported by the LHCb collaboration. Assuming that a four-bin scheme optimised on the models retains a similar sensitivity when applied in data, it is estimated that the statistical uncertainty on γ from the B-meson sample so far collected by the LHCb experiment will be as low as 5 degrees. This will be one of the most precise results available for any single decay mode in a B−→DK− measurement. Quantum-correlated DD¯ data accumulated by the CLEO-c experiment are analysed to provide first constraints on the coherence factors and average strong-phase differences in the four bins, which are necessary inputs for the measurement. These constraints are compared with the predictions of the model, and consequences for the measurement of γ are discussed.
Highlights
An important goal of flavour physics is to determine the angle γ = arg(− V ud ∗ ub / cd ∗ cb )of the Cabibbo-Maskawa-Kobayashi (CKM) Unitarity Triangle with the best possible precision
Sensitivity to this weak phase can be obtained by measuring CP -violating and associated observables in the decay B− → D K −, where D indicates a neutral charm meson reconstructed in a final state common to both D0 and D 0. (The inclusion of charge-conjugate processes is implied throughout, unless otherwise stated.) First measurements of γ using this strategy were performed at the B-factory experiments [1,2], but the most precise ensemble of results comes from the LHCb collaboration, which has exploited a wide selection of D-decay modes1 to establish γ = (74.0+−55..08)◦ [3]
All previous analyses of B− → D K −, D → K +π −π −π + decays have integrated over the phase space of the D meson, an approach which has limited the sensitivity that the measurement provides to the angle γ of the unitarity triangle
Summary
Of the Cabibbo-Maskawa-Kobayashi (CKM) Unitarity Triangle with the best possible precision. Reported the world’s first amplitude model of D0 → K +π −π −π + and a new model of the favoured D0 → K −π +π +π − mode that benefits from a much larger sample than available to any previous study In principle these models can be used directly in an unbinned B− → D K − measurement, thereby maximising the statistical precision of the analysis.
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